 If you liked
Toshokan no Daimajutsushi
|
 ...then you might like
Saihate no Solte
|
While their main plots are not particularly alike, both manga are very similar in regards to their absolutely fantastic world building. Each take you on a breathtaking adventure with unique settings, characters, and premises, leaving you (or just me at least), in awe.
They also both take place in a fantasy setting where you see the main characters grow, with tinges of sinister and mysterious things being at play. Especially if you liked the not-a-typical-isekai kind of fantasy adventure aspect of Toshokan no Daimajutsushi, then Saihate no Solte is definitely worth a read.